Background: Circulating tumor cells are cancer cells which separate from the primary tumor and enter systemic circulation. In this study, it was aimed to examine the relationship between circulating tumor cells isolated and identified from the peripheral blood of patients with pancreatobiliary cancer, with the clinicopathological characteristics of the patients and their overall survival. Methods: A total of 21 patients were included in the study. Density-gradient centrifugation with the OncoQuick® assay was performed for isolation of circulating tumor cells from peripheral blood. In order to identify circulating tumor cells, enriched samples underwent flow cytometric analysis. Results: The rate of patients with positive surgical margin in the high circulating tumor cell group (circulating tumor cell >15) was identi- fied to be statistically significantly high compared to the group with low circulating tumor cells (circulating tumor cell ≤15) (83.3% vs. 16.7%; P = .041). Median neutrophil/lymphocyte ratio was found to be higher in the high circulating tumor cell group compared to the low circulating tumor cell group, which was close to statistical significance (2.37 vs. 1.41; P = 0.055). Conclusions: Circulating tumor cells were identified to have a significant relationship with surgical margin positivity in our study for the first time, suggesting that the circulating tumor cells count in peripheral blood in preoperative patients may be a biomarker predicting positive surgical margin. Due to the very low number of studies assessing the relationship between circulating tumor cells and neutro- phil/lymphocyte ratio, our study which identified relationship close to statistical significance between circulating tumor cells and neu- trophil/lymphocyte ratio, significantly contributes to the literature on the topic of the possible role of lymphocytes in circulating tumor cell clearance. Keywords: Circulating tumor cells, pancreatobiliary cancer, prognosis